Drill collar Stabilizers

Downhole drilling tools are the components of the lower part of a drill string used in normal drilling operations such as the drill bits, drill collars, stabilizers, shock absorbers, hole openers, underreamers, drilling jars as well as a variety of drill stem subs. 

The drill string is defined here as a drill pipe with tool joints and drill collars. The drill stem consists of the drill string and other components of the drilling assembly that includes the kelly, subs, stabilizers, reamers as well as shock absorbers, and junk baskets or drilling jars used in certain drilling conditions. The drill stem (1) transmits power by rotary motion from the surface to a rock bit, (2) conveys drilling fluid to the rock bit, (3) produces the weight on bit for efficient rock destruction by the bit, and (4) provides control of borehole direction. 

Being aware of standardized drill collar sizes, an 11 or 12-in. drill collar should be selected. To avoid such large drill collar OD, a stabilizer or a proper-sized square drill collar (or a combination of the two) should be placed above the... 

As drill bits, drill collars and drill stem subs are discussed elsewhere this section regards shock absorbers, jars, underreamers, and stabilizers. 

Six-point bottom hole reamer. This type of reamer is run between the drill collars and the bit when more stabilization or greater reaming capacity is required. Drilling in crooked hole areas with a six-point reamer has proven to be very successful in preventing sharp changes in hole angles. 

To employ a restricted fulcrum effect one stabilizer is placed Just above the bit while second stabilizer is placed above the nonmagnetic drill collar. The hookup allows a gradual buildup of inclination with no abrupt changes. 

To prevent key-seating one stabilizer is placed directly above the top of drill collars. The configuration prevents drill collars wedging into a key seat during tripping out of the hole. 

To prevent differential sticking across depleted sands stabilizers are placed throughout the drill collar string. The area of contact between drill collars and hole is reduced, thus reducing the sticking force. 

Short radius wells are usually drilled from a cased or uncased vertical well. Articulated drill collars are used to drill to 90° or beyond. A second stabilized assembly is used to drill the rest of the hole, usually in 4-J or 6-J-in. diameter. 

Bottom-hole assembly (BHA) Assembly composed of the rock bit, stabilizers, reamers, drill collars, subs, etc., used at the bottom of the drillstring. 

Pendulum hookup A bit and drill collar with a stabilizer to attain the maximum effect of the pendulum. 

CTO consists of approximately 35-50% fatty acids, 15-55% rosin acids, and 5—35% unsaponifiable and neutral material. CTO can be used right away as a surfactant for oil and gas drilling applications or can previously be oxidized by blowing with air at a temperature of 120-130°C for 24h. It forms water-in-oil emulsions and stabilizes the oil-based drilling mud when pumped at high bottom-hole temperature under pressure through the kelly, drill pipe, drill collars, and drill bit (Figure 3B.11). It is then returned... 

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